1. Technical Field
This invention relates to the field of an apparatus for applying pulling force. More specifically the invention relates to an apparatus for the placement of conductive wire.
2. Background Art
Supplying buildings with electricity and communications capabilities involves threading lines, or cable, through conduit. Typically, the path that cable must travel through the conduit includes changes in elevation and turns around corners. Generally, the procedure used to run cable involves first threading lightweight flexible lines through the entire length of conduit. Heavier lines are then pulled through, by attaching them to one end of the lighter line and pulling the lighter line through at the other end of the conduit. This procedure may need to be repeated until a line is threaded which can bear the weight of the target cable, when is then attached and pulled through.
To thread heavier lines, lighter lines must be pulled through first. The pulling force required can be significant depending on the weight of the heavier lines and distance traveled. The pulling force can also increase with the bends and turns in the conduit. Thus, there is a need to substitute machine force for human force to reduce the human effort required in this procedure.
Others have substituted machine force for human force in pulling cable through conduit. Oleson, U.S. Pat. No. 3,190,616, discloses a cable threading apparatus. Newell, U.S. Pat. No. 3,968,952, discloses an assembly for pulling a line. Straight, U.S. Pat. No. 4,270,734, discloses a portable wire puller. Lucas, U.S. Pat. No. 4,456,225 discloses a cable pulling apparatus. Carter et al., U.S. Pat. No. 4,497,470, discloses a powered cart mounted cable puller.
Each of the named apparatus includes a dedicated motor; however, dedicating a motor in most cases adds bulk, weight, and cost. Therefore, the need to substitute machine force for human force in pulling wire without significant bulk, weight, and cost is not met by these apparatus.
Others have applied the use of hand-held power drills for winding. Cole, U.S. Pat. No. 4,196,864 discloses a line winding tool set. Sossamon, U.S. Pat. No. 4,951,890 discloses a drill-operated adapter for unwinding fishing lines from reels. Jones, U.S. Pat. No. 5,149,056 discloses a wire puller for electrical conduits.
These apparatus attach to a power drill, utilizing the power of the drill to pull cable and wind it onto spindles of various sizes and shapes. However, they are often insufficient for use with the various weights and lengths of cable threaded through conduit. Further, these apparatus share a problem, in that an operator must exert differing degrees of stabilizing force to hold the drill during the winding process. In summary, the prior art apparatus have proven to be cumbersome, and to be very limited in the capacity of line that may be wound onto their spindles.
It can be seen from the above discussion that it would be an improvement in the art to provide a line puller which can be driven by a multiple use motor so that the weight and cost of the apparatus is minimized. Also, it would be an improvement if the line puller could be positioned such that the operator does not have to exert a stabilizing force while the wire is pulled, and is not limited in line winding capacity.
The present invention provides an apparatus for pulling line through conduit, to which a power drill or other portable power tool may be attached as the motor force. The apparatus includes a frame having a drive shaft mounting portion, a power tool restraint portion, and an adjustable forearm portion, wherein the power tool restraint portion is adapted to register a portable rotary power tool, such as a power drill, with the frame. A drive shaft is mounted with the frame in the drive shaft mounting portion, wherein the drive shaft may be rotated about its longitudinal axis and a first end of the drive shaft is sized to be coupled with a rotary output of the power tool. A frame switch having an xe2x80x9coffxe2x80x9d position and an xe2x80x9conxe2x80x9d position may also be mounted on the frame, the frame switch engaging a power switch on the power tool when the frame switch is moved from the xe2x80x9coffxe2x80x9d position to the xe2x80x9conxe2x80x9d position and when such a tool is mounted in the restraint portion and coupled to the drive shaft. Alternatively, a separate switch not mounted to the frame, such as a foot pedal switch, may be used to selectively apply power to the tool box. The stand and frame can be disassembled for easy transport.
The wire pulling apparatus is located near a conduit opening, or junction box, through which the line is to be pulled. The power tool is positioned onto the wire pulling apparatus in an appropriate one of multiple available positions. For example, if the power tool is a power drill it is positioned such that the jaws of the drill fit around one end of the drive shaft, and such that the frame switch can be used to depress the trigger switch on the drill. The chuck of the drill is used to couple the drill jaws to the drive shaft. The drill switch lever of the frame switch is rotated to actuate the drill that turns the drive shaft. The line to be pulled is then wrapped at least once around a spool attached to the drive shaft and maintained taut by the wire puller operator, to allow the turning of the drive shaft to pull the line through the conduit or out of the junction box.
The forearm portion may be adjusted in length so that the wire puller may be adapted to fit various situations and requirements. A mounting bracket may be removably attached to the forearm portion such that it too may be adjusted, both angularly and longitudinally. The ends of the mounting bracket arms may be wedge-shaped so as to fit in confined spaces.
An adapter may be removably mounted on the wire puller and positioned such that it applies a force on the conduit or junction box directed opposite to the force tending to pull the wire, thus preventing the conduit or junction box from being moved out of the proper position when wire is being pulled through it. An embodiment of the adapter is generally semi-circular, with opposing arms which may be arcuate in shape. The semi-circular shape allows the wire to be easily inserted into and removed from the space within the arcuate arms at any point along the wire""s length. If desired, an adapter set comprising a series of adapters in a range of sizes may be provided. A possible size series is one where the adapters are designed to correspond to standard conduit diameters.